Ultrafine lanthanum zirconate powder and method for preparing the same

Abstract

The application provides a superfine lanthanum zirconate powder and a preparation method thereof, and belongs to the technical field of powder preparation. Soluble zirconium salt, soluble lanthanum salt and water are mixed to obtain a lanthanum zirconate solution; the lanthanum zirconate solution and a precipitant are added into a polyacrylic acid solution to perform a precipitation reaction, so as to obtain a precipitate; the precipitate is sequentially subjected to washing and calcination, so as to obtain the superfine lanthanum zirconate powder; the pH value of a washing liquid used in the washing is 8-8.5; and the temperature of the calcination is 1000-1200 DEG C. In the application, PAA is added as a dispersant to inhibit grain agglomeration; the lanthanum zirconate solution and the precipitant are added into the polyacrylic acid solution to perform the precipitation reaction; the pH value of the washing liquid is limited; and the temperature of the calcination is limited, so that the superfine nanometer lanthanum zirconate powder is prepared, the particle size is small, and the powder does not agglomerate.

Description

Technical Field

[0001] This invention relates to the field of powder preparation technology, and in particular to an ultrafine lanthanum zirconate powder and its preparation method. Background Technology

[0002] Lanthanum zirconate (La₂Zr₂O₇) possesses advantages such as good thermal stability, low thermal conductivity, and high radiation impedance, and is mainly used in high-temperature insulation, high-temperature catalyst supports, high-temperature superconducting buffer layers, and solid electrolytes. Particle size plays a crucial role in its application; smaller particle sizes result in larger specific surface areas and enhanced physical and chemical activity. Currently, industrial production mainly uses solid-state and precipitation methods for synthesis. Solid-state reaction methods require sintering at 1500℃ and holding at that temperature for a long time to obtain La₂Zr₂O₇ with a pyrochlore structure. The powder obtained by this method has uneven micro-mixing, with problems such as component segregation, uneven microstructure, and severe agglomeration. Precipitation methods, on the other hand, have lower reaction temperatures and lower costs, making them more suitable for industrial production. However, the precipitate is prone to agglomeration during precipitation, washing, filtration, and drying, resulting in larger powder particles with a D50 greater than 10 μm. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide an ultrafine lanthanum zirconate powder and its preparation method. The ultrafine lanthanum zirconate powder obtained by this invention has a small particle size and does not agglomerate.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing ultrafine lanthanum zirconate powder, comprising the following steps:

[0006] A lanthanum-zirconium solution is obtained by mixing a soluble zirconium salt, a soluble lanthanum salt, and water.

[0007] The lanthanum-zirconium solution and the precipitant were added to a polyacrylic acid (PAA) solution to carry out a precipitation reaction, thereby obtaining a precipitate;

[0008] The precipitate was washed and calcined sequentially to obtain the ultrafine lanthanum zirconate powder. The pH value of the washing solution used for washing was 8-8.5, and the calcination temperature was 1000-1200℃.

[0009] Preferably, the molar ratio of La to Zr in the lanthanum-zirconium solution is 1:1.

[0010] Preferably, the concentration of La in the lanthanum-zirconium solution is not greater than 1 mol / L.

[0011] Preferably, the concentration of the polyacrylic acid solution is 1~10 g / L.

[0012] Preferably, the volume ratio of the polyacrylic acid solution to the lanthanum zirconium solution is 1~2:1.

[0013] Preferably, the lanthanum-zirconium solution is added to the polyacrylic acid solution at a rate of 200-500 mL / min.

[0014] Preferably, the pH value of the system during the precipitation reaction is 8-12.

[0015] Preferably, the burning time is 2 to 6 hours.

[0016] Preferably, the molar ratio of the precipitant to the La element in the soluble lanthanum salt is 4~10:1.

[0017] The present invention also provides ultrafine lanthanum zirconate powder prepared by the preparation method described above, wherein the ultrafine lanthanum zirconate powder has a D50 of 400~600nm and a grain size of 20~100nm.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] This invention incorporates PAA as a dispersant to inhibit crystal agglomeration. Specifically, it specifies the addition of the lanthanum-zirconium solution and precipitant to a polyacrylic acid solution for precipitation, the pH value of the washing solution, and the calcination temperature, thereby producing ultrafine nano-lanthanum zirconate powder with small particle size and no agglomeration. Furthermore, the operation is simple, uses commonly used industrial raw materials, is low-cost, and the calcination temperature is 1000~1200℃, making it more energy-efficient and environmentally friendly. It holds promise for the industrial production of ultrafine nano-lanthanum zirconate.

[0020] The present invention also provides ultrafine lanthanum zirconate powder prepared by the preparation method described above, wherein the ultrafine lanthanum zirconate powder has a D50 of 400~600nm and a grain size of 20~100nm, which improves the problem of large particles easily formed by conventional precipitation method and makes the product an ultrafine nanoparticle. Attached Figure Description

[0021] Figure 1 Here is a SEM image of the ultrafine lanthanum zirconate powder prepared in Example 1;

[0022] Figure 2 The laser diffraction particle size distribution curve of the ultrafine lanthanum zirconate powder prepared in Example 1 is shown.

[0023] Figure 3 X-ray diffraction analysis diagram of the ultrafine lanthanum zirconate powder prepared in Example 1;

[0024] Figure 4 Here is a SEM image of the ultrafine lanthanum zirconate powder prepared in Example 2;

[0025] Figure 5The laser diffraction particle size distribution curve of the ultrafine lanthanum zirconate powder prepared in Example 2 is shown.

[0026] Figure 6 Here is a SEM image of the ultrafine lanthanum zirconate powder prepared in Example 3;

[0027] Figure 7 The laser diffraction particle size distribution curve of the ultrafine lanthanum zirconate powder prepared in Example 3 is shown.

[0028] Figure 8 The X-ray diffraction pattern of the powder prepared in Comparative Example 1 is shown.

[0029] Figure 9 SEM image of the powder prepared in Comparative Example 1;

[0030] Figure 10 SEM image of the powder prepared in Comparative Example 2;

[0031] Figure 11 SEM image of the powder prepared in Comparative Example 3;

[0032] Figure 12 The laser diffraction particle size distribution curve of the powder prepared in Comparative Example 4 is shown.

[0033] Figure 13 The laser diffraction particle size distribution curve of the powder prepared in Comparative Example 5 is shown. Detailed Implementation

[0034] This invention provides a method for preparing ultrafine lanthanum zirconate powder, comprising the following steps:

[0035] A lanthanum-zirconium solution is obtained by mixing a soluble zirconium salt, a soluble lanthanum salt, and water.

[0036] The lanthanum-zirconium solution and the precipitant were added to a polyacrylic acid solution to carry out a precipitation reaction, and a precipitate was obtained.

[0037] The precipitate was washed and calcined sequentially to obtain the ultrafine lanthanum zirconate powder. The pH value of the washing solution used for washing was 8-8.5, and the calcination temperature was 1000-1200℃.

[0038] Unless otherwise specified, all raw materials used in this invention are commercially available products in the field.

[0039] This invention involves mixing soluble zirconium salt, soluble lanthanum salt, and water to obtain a lanthanum-zirconium solution.

[0040] In this invention, the soluble zirconium salt preferably includes one or more of zirconium oxychloride, zirconium chloride, and zirconium nitrate.

[0041] In this invention, the soluble lanthanum salt preferably includes lanthanum chloride and / or lanthanum nitrate.

[0042] In this invention, the molar ratio of La to Zr in the lanthanum-zirconium solution is preferably 1:1.

[0043] The present invention preferably first prepares a soluble lanthanum salt aqueous solution, adds the soluble zirconium salt to the soluble lanthanum salt aqueous solution, and then adds water to obtain the lanthanum-zirconium solution.

[0044] In this invention, the concentration of La in the lanthanum-zirconium solution is preferably no greater than 1 mol / L, specifically 0.25, 0.5, or 1 mol / L.

[0045] After obtaining the lanthanum-zirconium solution, the present invention adds the lanthanum-zirconium solution and a precipitant to a polyacrylic acid solution to carry out a precipitation reaction, thereby obtaining a precipitate.

[0046] In this invention, the concentration of the polyacrylic acid solution is preferably 1~10 g / L, specifically 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 g / L.

[0047] In this invention, the volume ratio of the polyacrylic acid solution to the lanthanum zirconium solution is preferably 1 to 2:1, specifically 1:1, 20:15 or 2:1.

[0048] In this invention, the addition rate of the lanthanum-zirconium solution to the polyacrylic acid solution is preferably 200-500 mL / min, specifically 200, 300, 400 or 500 mL / min. The polyacrylic acid solution serves to disperse the particles, and by adding the lanthanum-zirconium solution to the polyacrylic acid solution, agglomeration into large particles is prevented, and the particle size is reduced.

[0049] In this invention, the lanthanum-zirconium solution and the precipitant are preferably added to the polyacrylic acid solution simultaneously, and then stirred to carry out the precipitation reaction.

[0050] In this invention, the stirring speed is preferably 150~250 rpm, specifically 150, 200 or 250 rpm.

[0051] In this invention, the precipitant is preferably ammonia water and / or ammonium bicarbonate solution, and the concentration of the precipitant is preferably 2~3 mol / L.

[0052] In this invention, the molar ratio of the precipitant to La is preferably 4 to 10:1, specifically 4:1, 6:1, 8:1, 9.6:1 or 10:1.

[0053] In this invention, the pH value of the system during the precipitation reaction is preferably 8 to 12, specifically 8, 9, 10, 11 or 12. In this invention, the pH value of the system during precipitation is preferably controlled by adjusting the flow rate of the precipitant.

[0054] In this invention, the temperature of the precipitation reaction is preferably room temperature, and the time is preferably 30 to 120 minutes, specifically 30, 60, 90 or 120 minutes.

[0055] After the precipitation reaction is completed, the present invention preferably removes the mother liquor by filtration to obtain the precipitate.

[0056] After obtaining the precipitate, the present invention washes and calcines the precipitate sequentially to obtain the ultrafine lanthanum zirconate powder. The pH value of the washing solution used for washing is 8~8.5, specifically 8 or 8.5, and the calcination temperature is 1000~1200℃, specifically 1000, 1100 or 1200℃.

[0057] The present invention preferably uses ammonia water to adjust the pH value of deionized water to obtain the washing solution.

[0058] The present invention does not impose any special limitations on the specific parameters of the washing process; any method known to those skilled in the art can be used.

[0059] After the washing process is completed, the present invention preferably microwave-dries the resulting washed material before performing the calcination. The present invention does not have specific limitations on the specific parameters of the microwave drying process, as long as complete drying is achieved.

[0060] In this invention, the burning time is preferably 2 to 6 hours, specifically 2, 3, 4, 5 or 6 hours.

[0061] The present invention also provides ultrafine lanthanum zirconate powder prepared by the preparation method described above, wherein the D50 of the ultrafine lanthanum zirconate powder is 400~600nm, specifically 471, 580 or 583nm, and the grain size is 20~100nm.

[0062] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0063] Example 1

[0064] 3.75 mol of zirconium oxychloride was dissolved in a lanthanum chloride solution (containing 3.75 mol of lanthanum chloride), and deionized water was added to bring the volume to 15 L, resulting in a Zr concentration of 0.25 mol / L. The lanthanum-zirconium solution was added to 20 L of a 3 g / L PAA solution at a rate of 500 mL / min, while simultaneously adding 3 mol / L ammonia solution. The ammonia flow rate was adjusted (average rate 400 mL / min) to maintain the pH of the system between 8 and 8.5. The total volume of ammonia added was 12 L. The precipitation time was 30 min, and the stirring speed during precipitation was 250 rpm. After the precipitation reaction was completed, the mother liquor was immediately filtered, washed with weakly alkaline water (pH 8, obtained by adjusting the pH of deionized water with ammonia), microwave-dried, and then calcined at 1000℃ for 6 h to obtain ultrafine lanthanum zirconate powder. Figure 1 The image shows a SEM image of the ultrafine lanthanum zirconate powder prepared in Example 1, indicating that the grain size is 20~100 nm. Figure 2 The laser diffraction particle size distribution curve of the ultrafine lanthanum zirconate powder prepared in Example 1 shows that the D50 is 0.583 µm. Figure 3 The X-ray diffraction pattern of the ultrafine lanthanum zirconate powder prepared in Example 1 shows that the phase is lanthanum zirconate La2Zr2O7.

[0065] Example 2

[0066] 7.5 mol of zirconium chloride was dissolved in a lanthanum chloride solution (containing 7.5 mol of lanthanum chloride), and deionized water was added to bring the volume to 15 L, resulting in a Zr concentration of 0.5 mol / L. The lanthanum-zirconium solution was added to 20 L of a 5 g / L PAA solution at a rate of 250 mL / min, along with a 2 mol / L ammonium bicarbonate solution. The flow rate of the ammonium bicarbonate solution was adjusted (average rate 250 mL / min) to maintain the pH of the system at 8–8.5. The total volume of ammonium bicarbonate solution added was 15 L. The precipitation time was 60 min, and the stirring speed during precipitation was 250 rpm. After the precipitation reaction was complete, the mother liquor was immediately filtered, washed with weakly alkaline water (pH 8, obtained by adjusting the pH of deionized water with ammonia), microwave-dried, and then calcined at 1000 °C for 4 h to obtain ultrafine lanthanum zirconate powder. Figure 4 The image shows a SEM image of the ultrafine lanthanum zirconate powder prepared in Example 2, indicating that the grain size is 20~100 nm. Figure 5 The laser diffraction particle size distribution curve of the ultrafine lanthanum zirconate powder prepared in Example 2 shows that D50 is 0.580µm. X-ray diffraction analysis of the ultrafine lanthanum zirconate powder prepared in Example 2 shows that the phase is lanthanum zirconate La2Zr2O7.

[0067] Example 3

[0068] 24 mol of zirconium oxychloride was dissolved in lanthanum nitrate solution (24 mol of lanthanum nitrate), and deionized water was added to a final volume of 24 L, resulting in a Zr concentration of 1 mol / L. The lanthanum-zirconium solution was added to 20 L of 10 g / L PAA solution at a rate of 200 mL / min. Simultaneously, a mixed solution consisting of 24 L of 3 mol / L ammonium bicarbonate solution and 24 L of 1 mol / L ammonia solution was added. The flow rate of the mixed solution was adjusted (average flow rate 480 mL / min) to maintain the pH of the system at 8–8.5. The precipitation time was 120 min, and the stirring speed during precipitation was 250 rpm. After the precipitation reaction was completed, the mother liquor was immediately filtered, washed with weakly alkaline water (pH 8.5, obtained by adjusting the pH of deionized water with ammonia), microwave-dried, and then calcined at 1200℃ for 4 h to obtain ultrafine lanthanum zirconate powder. Figure 6 The image shows a SEM image of the ultrafine lanthanum zirconate powder prepared in Example 3, indicating that the grain size is 20~100 nm. Figure 7 The laser diffraction particle size distribution curve of the ultrafine lanthanum zirconate powder prepared in Example 3 shows that the D50 is 0.471µm. X-ray diffraction analysis of the ultrafine lanthanum zirconate powder prepared in Example 3 shows that the phase is lanthanum zirconate La2Zr2O7.

[0069] Comparative Example 1

[0070] Same as Example 1, except that the pH value during precipitation was 7.5 and the calcination temperature was 850°C. The X-ray diffraction analysis of the obtained powder is as follows: Figure 8 As shown, the phases are LaOCl, ZrO2, and La2Zr2O7. Figure 9 The SEM image of the powder in Comparative Example 1 shows that the prepared powder consists of micron-sized particles.

[0071] Comparative Example 2

[0072] Same as Example 1, except that the PAA solution is replaced with deionized water during the precipitation reaction and the washing is also done with deionized water. Figure 10 The SEM image of the powder obtained in Comparative Example 2 shows that the powder consists of micron-sized particles.

[0073] Comparative Example 3

[0074] Similar to Example 1, the only difference being that ammonia was added to the lanthanum-zirconium solution, and the precipitation reaction was carried out for 5 minutes at a system pH of 8.5. Figure 11 The SEM image of the powder prepared in Comparative Example 3 shows that the powder consists of micron-sized particles.

[0075] Comparative Example 4

[0076] Similar to Example 1, except that deionized water and alcohol were used for washing, and the powder was dried in a forced-air drying oven at 120°C. The median diameter (D50) of the resulting powder was measured using a laser particle size analyzer. Figure 12 The laser diffraction particle size distribution curve of the powder prepared in Comparative Example 4 is shown, with a D50 of 48.48 μm.

[0077] Comparative Example 5

[0078] Similar to Example 1, the only difference is that the lanthanum-zirconium solution was added to ammonia water, and the addition was stopped when the pH of the system reached 8.5. The addition time was 0.5 h, and stirring was continued for 1 h after the addition was completed. The powder was washed with deionized water and alcohol, and the median diameter D50 of the obtained powder was measured by a laser particle size analyzer. Figure 13 The laser diffraction particle size distribution curve of the powder prepared in Comparative Example 5 is shown, with a D50 of 15.24 μm.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing ultrafine lanthanum zirconate powder, characterized in that, Includes the following steps: A lanthanum-zirconium solution is obtained by mixing a soluble zirconium salt, a soluble lanthanum salt, and water. The lanthanum-zirconium solution and the precipitant were added to a polyacrylic acid solution to carry out a precipitation reaction, and a precipitate was obtained. The precipitate was washed and calcined sequentially to obtain the ultrafine lanthanum zirconate powder. The pH value of the washing solution used for washing was 8-8.5, and the calcination temperature was 1000-1200℃. The concentration of the polyacrylic acid solution is 1~10 g / L; The volume ratio of the polyacrylic acid solution to the lanthanum zirconium solution is 1~2:1; The lanthanum-zirconium solution is added to the polyacrylic acid solution at a rate of 200-500 mL / min.

2. The preparation method according to claim 1, characterized in that, The molar ratio of La to Zr in the lanthanum-zirconium solution is 1:

1.

3. The preparation method according to claim 1 or 2, characterized in that, The concentration of La in the lanthanum-zirconium solution is no greater than 1 mol / L.

4. The preparation method according to claim 1, characterized in that, The pH value of the system during the precipitation reaction is 8~12.

5. The preparation method according to claim 1, characterized in that, The burning time is 2 to 6 hours.

6. The preparation method according to claim 1, characterized in that, The molar ratio of the precipitant to the La element in the soluble lanthanum salt is 4~10:

1.

7. The ultrafine lanthanum zirconate powder prepared by the preparation method according to any one of claims 1 to 6, characterized in that, The ultrafine lanthanum zirconate powder has a D50 of 400~600nm and a grain size of 20~100nm.

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